MgO-Y2O3红外透明陶瓷制备与微波烧结机理研究

MgO-Y2O3 infrared transparent ceramics have recently acquired a high degree of research interest for midwave infrared window materials due to their excellent mechanical properties, thermal shock resistance and infrared transmittance.?Sintering densification behavior and microstructure of MgO-Y2O3 infrared transparent ceramics have a great influence on the infrared transmittance. In this study, MgO-Y2O3 nanopowders are synthesized by sol-gel combined microwave heating technology, and MgO-Y2O3 infrared transparent ceramics are sintered by microwave sintering process. We will study the densification behavior, microstructure as well as microwave sintering mechanism of MgO-Y2O3 infrared transparent ceramics. Moreover, the effect of microwave sintering processing on microstructure and infrared transmittance, and the comparation of microwave sintering with conventional sintering processing will be investigated. The objectives of this project are to solve the key scientific problems related to the microwave sintering of MgO-Y2O3 infrared transparent ceramics, and to establish a science base for the preparation of high performance?MgO-Y2O3 midwave infrared window materias.

MgO-Y2O3透明陶瓷是目前最有发展潜力的一种新型中红外窗口材料，它具有优良的力学性能、抗热冲击性能和中红外透过性能。MgO-Y2O3红外透明陶瓷的烧结致密化行为和微观结构对其红外透过率有极大影响。本课题以溶胶凝胶-微波加热法合成MgO-Y2O3纳米粉体，采用微波烧结工艺制备MgO-Y2O3红外透明陶瓷。研究用作红外窗口材料的MgO-Y2O3红外透明陶瓷的微波烧结致密化过程和微观结构，探讨MgO-Y2O3红外透明陶瓷的微波烧结机理，找出烧结条件对微观结构和红外透过性能的相关性规律，探讨微波烧结与传统烧结机理的区别，解决MgO-Y2O3红外透明陶瓷微波烧结制备中的关键科学问题，为高性能中红外MgO-Y2O3窗口材料的制备和应用奠定科学基础。

本项目采用溶胶-凝胶法和微波诱导燃烧法合成了MgO-Y2O3纳米粉体，然后以微波诱导燃烧法合成的MgO-Y2O3纳米粉体为原料，分别采用传统烧结工艺和微波烧结工艺制备了MgO-Y2O3复合陶瓷，并研究了坯体的致密化过程。最后采用微波两步烧结工艺制备了亚微米MgO-Y2O3复合陶瓷，研究了复合陶瓷的力学性能和红外透过性能。研究结果表明：.（1）微波诱导燃烧法合成的粉体分散性良好，平均粒径在30 nm以下，比表面积为35.6 m2/g。与溶胶凝胶法合成的粉体相比，微波诱导燃烧法合成的粉体具有更高的活性。 .（2）对于微波烧结，MgO-Y2O3复合陶瓷的晶粒生长机制主要为晶界扩散，反应烧结活化能为108.22 kJ/mol。相对于传统烧结，微波烧结能降低反应烧结活化能，进而降低烧结温度，通过晶界扩散的晶粒生长机制有利于获得细化的晶粒结构。微波烧结工艺中的升温速度、烧结温度和保温时间对MgO-Y2O3复合陶瓷烧结有重要影响，以10℃/min的升温速率升温至1400℃并保温2 h，所制备的MgO-Y2O3复合陶瓷的相对密度可达99.6%。.（3）采用微波两步法烧结工艺的最佳工艺参数为：以10℃/min的升温速度升温至1375℃，.保温1 min，然后以10℃/min的速率降温至1300℃，保温2 h。所制备的MgO-Y2O3复合陶瓷的平均晶粒尺寸约为800 nm，相对密度为99.7%，维氏硬度为11.7±0.3 GPa，在3~5 μm波段内的红外透过率为50~60%。